A storage device includes a plurality of storages. One storage (work storage) makes a copy of itself in another storage (back up storage) and thereby backs itself up. Among a plurality of storage devices arranged in locations that are remote from each other, one of the storage devices has a remote copying function of copying the data of the one storage device to another storage device.
An example of the related art is disclosed in Japanese Laid-open Patent Publication No. 2006-260292.